SYSCONF(3) NetBSD Library Functions Manual SYSCONF(3)
NAMEsysconf -- get configurable system variables
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS#include <unistd.h>longsysconf(int name);
DESCRIPTION
This interface is defined by IEEE Std 1003.1-1988 (``POSIX.1''). A far
more complete interface is available using sysctl(3).
The sysconf() function provides a method for applications to determine
the current value of a configurable system limit or option variable. The
name argument specifies the system variable to be queried. Symbolic con-
stants for each name value are found in the include file <unistd.h>.
The available values are as follows:
_SC_ARG_MAX
The maximum bytes of argument to execve(2).
_SC_ATEXIT_MAX
The maxmimum number of functions that may be registered with
atexit(3).
_SC_BARRIERS
The version of IEEE Std 1003.1 (``POSIX.1'') and its Barriers
option to which the system attempts to conform, otherwise -1.
_SC_CLOCK_SELECTION
Return the POSIX version the implementation of the Clock Selec-
tion Option on this system conforms to, or -1 if unavailable.
_SC_CHILD_MAX
The maximum number of simultaneous processes per user id.
_SC_CLK_TCK
The number of clock ticks per second.
_SC_FSYNC
Return 1 if the File Synchronization Option is available on this
system, otherwise -1.
_SC_HOST_NAME_MAX
The maximum size of a hostname, including NULL.
_SC_IOV_MAX
The maximum number of iovec structures that a process has avail-
able for use with preadv(2), pwritev(2), readv(2), recvmsg(2),
sendmsg(2) or writev(2).
_SC_JOB_CONTROL
Return 1 if job control is available on this system, otherwise
-1.
_SC_LOGIN_NAME_MAX
Returns the size of the storage required for a login name, in
bytes, including the terminating NUL.
_SC_MAPPED_FILES
Return 1 if the Memory Mapped Files Option is available on this
system, otherwise -1.
_SC_MEMLOCK
Return 1 if the Process Memory Locking Option is available on
this system, otherwise -1.
_SC_MEMLOCK_RANGE
Return 1 if the Range Memory Locking Option is available on this
system, otherwise -1.
_SC_MEMORY_PROTECTION
Return 1 if the Memory Protection Option is available on this
system, otherwise -1.
_SC_MONOTONIC_CLOCK
Return the POSIX version the implementation of the Monotonic
Clock Option on this system conforms to, or -1 if unavailable.
_SC_NGROUPS_MAX
The maximum number of supplemental groups.
_SC_OPEN_MAX
The maximum number of open files per process.
_SC_PAGESIZE
The size of a system page in bytes.
_SC_PASS_MAX
The maximum length of the password, not counting NULL.
_SC_READER_WRITER_LOCKS
The version of IEEE Std 1003.1 (``POSIX.1'') and its Read-Write
Locks option to which the system attempts to conform, otherwise
-1.
_SC_REGEXP
Return 1 if POSIX regular expressions are available on this sys-
tem, otherwise -1.
_SC_SEMAPHORES
The version of IEEE Std 1003.1 (``POSIX.1'') and its Semaphores
option to which the system attempts to conform, otherwise -1.
Availability of the Semaphores option depends on the
P1003_1B_SEMAPHORE kernel option.
_SC_SHELL
Return 1 if POSIX shell is available on this system, otherwise
-1.
_SC_SPIN_LOCKS
The version of IEEE Std 1003.1 (``POSIX.1'') and its Spin Locks
option to which the system attempts to conform, otherwise -1.
_SC_STREAM_MAX
The minimum maximum number of streams that a process may have
open at any one time.
_SC_SYMLOOP_MAX
The maximum number of symbolic links that may be expanded in a
path name.
_SC_SYNCHRONIZED_IO
Return 1 if the Synchronized I/O Option is available on this sys-
tem, otherwise -1.
_SC_THREADS
The version of IEEE Std 1003.1 (``POSIX.1'') and its Threads
option to which the system attempts to conform, otherwise -1.
_SC_TIMERS
The version of IEEE Std 1003.1 (``POSIX.1'') and its Timers
option to which the system attempts to conform, otherwise -1.
_SC_TZNAME_MAX
The minimum maximum number of types supported for the name of a
timezone.
_SC_SAVED_IDS
Returns 1 if saved set-group and saved set-user ID is available,
otherwise -1.
_SC_VERSION
The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
attempts to comply.
_SC_XOPEN_SHM
Return 1 if the X/Open Portability Guide Issue 4, Version 2
(``XPG4.2'') Shared Memory option is available on this system,
otherwise -1.
Availability of the Shared Memory option depends on the SYSVSHM
kernel option.
_SC_BC_BASE_MAX
The maximum ibase/obase values in the bc(1) utility.
_SC_BC_DIM_MAX
The maximum array size in the bc(1) utility.
_SC_BC_SCALE_MAX
The maximum scale value in the bc(1) utility.
_SC_BC_STRING_MAX
The maximum string length in the bc(1) utility.
_SC_COLL_WEIGHTS_MAX
The maximum number of weights that can be assigned to any entry
of the LC_COLLATE order keyword in the locale definition file.
_SC_EXPR_NEST_MAX
The maximum number of expressions that can be nested within
parenthesis by the expr(1) utility.
_SC_LINE_MAX
The maximum length in bytes of a text-processing utility's input
line.
_SC_RE_DUP_MAX
The maximum number of repeated occurrences of a regular expres-
sion permitted when using interval notation.
_SC_2_VERSION
The version of POSIX 1003.2 with which the system attempts to
comply.
_SC_2_C_BIND
Return 1 if the system's C-language development facilities sup-
port the C-Language Bindings Option, otherwise -1.
_SC_2_C_DEV
Return 1 if the system supports the C-Language Development Utili-
ties Option, otherwise -1.
_SC_2_CHAR_TERM
Return 1 if the system supports at least one terminal type capa-
ble of all operations described in POSIX 1003.2, otherwise -1.
_SC_2_FORT_DEV
Return 1 if the system supports the FORTRAN Development Utilities
Option, otherwise -1.
_SC_2_FORT_RUN
Return 1 if the system supports the FORTRAN Runtime Utilities
Option, otherwise -1.
_SC_2_LOCALEDEF
Return 1 if the system supports the creation of locales, other-
wise -1.
_SC_2_SW_DEV
Return 1 if the system supports the Software Development Utili-
ties Option, otherwise -1.
_SC_2_UPE
Return 1 if the system supports the User Portability Utilities
Option, otherwise -1.
_SC_GETGR_R_SIZE_MAX
The minimum size of the buffer passed to getgrgid_r(3) and
getgrnam_r(3).
_SC_GETPW_R_SIZE_MAX
The minimum size of the buffer passed to getpwnam_r(3) and
getpwuid_r(3).
_SC_NPROCESSORS_CONF
The number of processors configured.
_SC_NPROCESSORS_ONLN
The number of processors online (capable of running processes).
RETURN VALUES
If the call to sysconf is not successful, -1 is returned and errno is set
appropriately. Otherwise, if the variable is associated with functional-
ity that is not supported, -1 is returned and errno is not modified.
Otherwise, the current variable value is returned.
ERRORS
The sysconf() function may fail and set errno for any of the errors spec-
ified for the library functions sysctl(3). In addition, the following
error may be reported:
[EINVAL] The value of the name argument is invalid.
SEE ALSOsysctl(3)STANDARDS
The sysconf() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').
The constants _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are not part
of the standard, but are provided by many systems.
HISTORY
The sysconf function first appeared in 4.4BSD.
BUGS
The value for _SC_STREAM_MAX is a minimum maximum, and required to be the
same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously small
and misleading number.
NetBSD 5.0.1 August 14, 2006 NetBSD 5.0.1

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